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Stephen Donell - 7 - 31 January 2014 4. Appendix F indicates that sample MW-7-5 duplicate (lab sample ID 130531-117) experienced a 4-Bromofluoromethane surrogate failure of 67% recovery due to matrix interference; however, sample MW-7-5 (lab sample ID 130531-95) was analyzed in a separate QA/QC batch than its duplicate, which means the sample is not an actual duplicate. Sample MW-7-5 (lab sample ID 130531-95) did not experience the same degree of matrix interference as its duplicate with an acceptable 70% recovery result. In this case, Regional Water Board is concerned that the original and duplicate samples do not appear to have been analyzed in the same laboratory QA/QC batch which negates the duplicity of the samples. In addition, please discuss whether the laboratory verified the matrix interference source was from the sample with a re-test. 5. Appendix F indicates that sample TW-2-5 (lab sample ID 130531-138) experienced a toluene-d8 surrogate failure of 51% recovery due to matrix interference during EPA Method 8260B QA/QC. The toluene LCS analysis was within acceptable ranges. However, please indicate if the laboratory verified the matrix interference source was the sample with a re-test. Conclusions Even though previous investigations, in general, found higher concentrations of CDCs, the results of this investigation found elevated concentrations of 1,2-DCP, DBCP, nitrates, chloride, TDS, arsenic, diesel and motor oil range TPH that may require remedial action after additional Site characterization. Due to sampling errors, incomplete site drainage assessment and QA/QC problems, staff cannot completely assess the extent of soil and groundwater contamination with confidence. However, the Report documents the presence of sufficient Site contamination that the Site does not qualify for a determination of No Further Action. Site Assessment Report Staff of the Regional Water Board find that the Report is incomplete as discussed in the comments above. By 28 February 2014, please submit a revised Report that includes: 1. Lab sheets in the Appendices and groundwater TPH results in a Report summary table. 2. Sampling dates for all samples in Appendix A. 3. A discussion of why high PID samples from the monitoring and temporary well borings were not analyzed. 4. A clarification of data point locations in the discussion of prior investigations. 5. The catch basin discussion moved from section 4.2.4, Survey of Groundwater Monitoring Wells, to section 4.4 Site Topography and Surface Drainage. 6. Catch Basin Survey notes for Catch Basin 7, if available. 7. Reporting of TOC in units of milligrams per liter (mg/L) or micrograms per liter (ug/L).